Time-delay relay circuit



June 23, 1959 HUGE 2,892,133

I TIME-DELAY RELAY- CIRCUIT Filed July 19, 1955 I I 23w :/II5

25 v AC u 2 E l n ,7 SOURCE 1 INVEN TOR. HENRY M. HUGE Fig.4 Q MBM 1%United States Patent TIME-DELAY RELAY CIRCUIT Henry M. Huge, BayVillage, Ohio, assignor to Lorain Products Corporation, a corporation of(Phio Application July 19, 1955, Serial No. 523,001

6 Claims. (Cl. 3 17 -141) This invention relates to a means forcontrolling the operate time of a relay independently of its releasetime, by the use of a capacitor and resistor together with one or morerectifying elements. The circuit also embodies a marginal feature, sothat the operate voltage and release voltage of the relay areindependently adjustable.

The relay circuit of my invention is particularly suited for use withdevices which are operated from commercial A.-C. power when it isavailable and from a source of standby power when the commercial A.-C.power fails. One of the requirements of this application is that thetransfer from the normal A.-C. source to the standby source be as rapidas possible upon failure of the normal source. It is also important thatthe transfer to the standby source be efiected if the voltage of thenormal source falls below the minimum value at which satisfactoryoperation of the equipment is obtainable.

When interruptions of the commercial A.-C. power occur, the A.-C-.voltage frequently is erratic, remaining normal for a few seconds afterinterruption, and then failing again either partially or completely. itis highly desirable that the transfer device should not attempt tofollow these rapid interruptions and return of normal power, but shouldkeep the equipment running on the standby source of power until thenormal power source has been restored for a sufiicient period of time toindicate its probable permanent restoration; Prior devices designed forthis service have made use of a number of relays and one or more timingdevices. It is an obiect of my invention to provide a transfer relaycircuit meeting the requirements just outlined with a single relay,making use of capacitors for time delay.

It is also an object of my invention to provide a timedelay relay.circuit in which the operate time and release time of the relay areindependently adjustable, and particularly so that the delay onoperation of the relay may be long and the delay on release may beextremely short.

Another object of my invention is to provide a marginalrelay circuit inwhich the operate value and release value of the relay are independentlyadjustable, and in which the operation of the relay is delayed for apredetermined time after the application of power to the circu1t.

Another object of my invention is to provide a simple 1and inexpensivetime delay for an alternating current re- A further object of myinvention is to utilize the charging of a condenser to delay theoperation of a relay, without having the release of the relay delayed bythe discharge of the same condenser.

Another object of my invention is to provide a time delay relay circuitin which the release of the relay is instantaneous upon interruption ofpower to the circuit and in which the release of the relay is delayedwhen the input voltage to the circuit falls only slightly below themarginal release value.

An additional object of my invention is to provide 2,892,133 PatentedJune 23, 1959 with a single relay a time delay circuit in which delayedoperation of the relay is obtained regardless of how brief the powerinterruption may be.

Other objects and a better understanding of my invention may be obtainedby referring to the following specification and claims in connectionwith the accompanying drawings in which:

Figure 1 is an embodiment of my invention operating from a source ofdirect current.

Figure 2 is a modification of the arrangement shown in Figure 1operating from an alternating current source and utilizing a full wavebridge rectifier.

Figure 3 is an embodiment of my invention arranged for delaying theoperation of an A.-C. relay.

Figure 4 is a modification of the arrangement shown in Figure 2utilizing a full-wave bridge rectifier adapted to be energized from analternating current source.

Specifically, Figure 1 shows a relay 14 energized from a direct currentsource 10 through series resistors 12 and 13. Capacitor 18 is connectedin parallel with relay 14. The winding of relay 14 is also shunted bythe series combination of capacitor 17 and half-wave rectifier 1S.Resistor 16 is connected in parallel with capacitor 1'7.

The contacts 21 and 22 are operated by the relay 14' would sense thistrouble and take care of the power transfer of a device from normalcommercial power to a standby source of power through contacts 21 and22. It is to be understood that my novel circuit is not limited to theuse of transferring the operation of a device from a normal source ofpower over to a standby source of power, but may be used for manypurposes. My novel circuit, as will be explained later, provides forgiving reliable operation when transferring from normal source tostandby source.

The operation of the relay circuit shown in Figure l is briefly asfollows:

Assume that capacitors 17 and 18 are fully discharged and switch 11 isthen closed. Capacitor 17 will charge at anexponential rate to a finalvoltage equal to the steady-state voltage drop across resistor 16. Atthe same time, the voltage across the winding of relay 14 will alsoincrease at an exponential rate until it reaches the voltage at whichthe relay operates. When the relay operates, the back contact 19 opens,removing the short-circuit from across resistor 13.

The insertion of resistor 13 in the relay circuit has a tendency tolower the voltage across the winding of relay 14. With certain types ofrelay construction, this may cause the relay contacts to buzz andprevent complete operation of the relay. In order to maintain sufiicientvoltage across the relay coil to make it operate positively, thecapacitor 18 is added to the circuit. The charge stored on capacitor 18prevents an instantaneous drop of voltage across the relay winding 14and assures positive operation of the relay. In addition, the capacitor18 can be increased in size to provide a delay in the release of therelay 14. Positive relay action is also aided by another factor. Thevoltage drop through resistor 12 during the time delay period is due ina large part to the charging current being drawn by capacitor 17 throughthe half wave rectifier 15. When the additional resistor 13 is insertedin the circuit by the opening of relay contact 19, the initial drop involtage across the winding of relay 14 may be very small even ifcapacitor 18 is omitted from the circuit. This is true because as soonas the voltage across the winding of relay 14 drops, the voltage acrosscapacitor 17 becomes larger than the voltage across the winding of relay14. Under this condition, the half-wave rectifier 15 prevents dischargeof capacitor 17 through the relay winding, but, during the time thatcapacitor 17 is discharging through resistor 16, the parallelcombination of capacitor 17 and resistor 16 draws no current from thesource 10. As a result, the drop in voltage upon opening of the relaycontact 19 is much less than would normally be obtained, and thepositive relay action can be obtained even if capacitor 13 is omittedfrom the circuit, provided the mechanical construction of relay 14 issuitable for this purpose.

Resistor 13 is adjusted to provide the required release value in therelay circuit. By adjustment of the resistor 13, the release voltage ofthe relay can be brought as near as required to the operate voltage. Aspreviously mentioned, the voltage across the winding of relay 14 doesnot immediately drop to its final value upon opening of relay contact 19but falls gradually as capacitor 17 discharges through resistor 16.Because of this fact, a momentary drop in the voltage of source belowthe voltage at which the relay is adjusted to release in a steady statecondition will not cause a release of the relay. In case of a momenarydrop in the voltage of source 10 the distribution of voltage between therelay 14 and the dropping resistors 12 and 13 is changed by the energystored in capacitor 17. However, in case of a complete failure ofvoltage from source 10 as when switch 11 is open, the relay 14 iscompletely de-energized except for the charge stored on capacitor 18.The charge stored on capacitor 17 is prevented from discharging throughthe relay windings by the half-wave rectifier 15. The time delay onoperation of the relay is proportional to the sum of the capacitors 17and 18, whereas the time delay on release of the relay depends only oncapacitor 18 which may be made as small as required, or even omittedwhen the mechanical construction of the relay provides the positiverelay action previously described. By means of this circuit, I am,therefore, able to obtain an extremely long delay on operation of therelay 14 and a practically instantaneous release of the relay when thecircuit is de-energized.

The circuit shown in Figure 1 has another extremely valuablecharacteristic. After the relay 14 operates, the voltage acrosscapacitor 17 drops as the capacitor discharges through resistor 16 untilthe voltage across capacitor 17 becomes substantially the same as thatacross relay 14. This voltage will normally approach the release voltageof the relay 14, as adjusted by resistor 13, and may be considerablyless than the operate voltage of the relay. After the steady statecondition has been reached, with the relay operated, if the relay isreleased by a momentary opening of the switch 11, the switch then beingreclosed, substantially the entire time delay of the circuit will beobtained before the relay again operates, because the capacitor 17 mustbe recharged from the release voltage of the relay 14 to the operatevoltage of relay 14 before the relay 14 can again op crate.

Figure 2 shows a modification of the circuit shown in Figure 1 utilizinga full-wave rectifier 25 to supply direct current to the circuit fromalternating current source 38. The series resistor 13 in Figure 1 isreplaced by a shunt resistor 28 in Figure 2.

The shunt resistor 28 is connected through the normally open contact 20of relay 14, so that when relay 14 operates, additional current ispassed through resistor 12 dropping the voltage to relay 14, providingoperating conditions similar to those in Figure 1.

In the circuit of Figure 2, resistor 28 is not introduced into thecircuit until the relay armature has almost completed its travel and thefront contact 20 of relay 14 is closed. This is particularlyadvantageous when capacitor 4 18 is to be made very small or omitted toobtain rapid release of the relay, as positive relay action is moreeasily obtained if the relay voltage is not reduced until the relayarmature has almost completed its travel.

Figure 3 is a circuit diagram of an arrangement for delaying theoperation of an A.-C. relay. The resistor or impedance element 12 inFigure 3 provides the voltage drop to delay the operation of the A.-C.relay 27 until capacitor 17 has been charged through the rectifier 26.If marginal relay operation is required, it can be obtained through theuse of the resistor or impedance element 13 controlled by the backcontact 19 of relay 27 as in Figure l. The operation of the circuit ofFigure 3 is similar to that of Figure 1 except that in Figure 3 there isno provision for delaying the release of the relay after switch 11 isopened.

Figure 4 is a circuit diagram of an arrangement using the full wavebridge rectifier 25 energized from an A.-C. source 38 through a resistoror impedance element 12 and a switch 11. Resistor 28 is connected inparallel with rectifier 25 through the normally open contact 20 of relay14. Rectifier 25 supplies current to the parallel combination of relay14 and capacitor 18, as well as to the parallel combination of resistor16 and capacitor 17 through the half-Wave rectifier 15.

The chief differences between Figure 4 and Figure 2 are that therectifier 25 in Figure 4 may be of a lower voltage rating because theelement 12 is in the A.-C. circuit, and the elements 12 and 28 in Figure4 may be reactive rather than resistive to reduce the power consumptionof the circuit.

Where marginal relay operation and maximum time delay with brief powerinterruptions are not required, the resistor 13 can be omitted fromFigures 1 and 3 and resistor 28 can be omitted from Figures 2 and 4.

Although I have described my invention with a certain degree ofparticularity, it is to be understood that the present disclosure hasbeen made only by way of example and that numerous changes in thedetails of construction and the combination and arrangement of parts maybe resorted to without departing from the spirit and scope of theinvention as herein claimed.

What is claimed is:

1. In combination, a relay having a winding and a contact, said relaybeing operable to close said contact when the voltage across saidwinding is of an operating value and being operable to open said contactwhen the voltage across said winding is below a release value, ahalf-wave rectifier, a second rectifier, a first capacitor, a secondcapacitor connected across said relay winding, a first resistor, asecond resistor, and a third resistor, first circuit means forenergizing said relay winding and said second capacitor from analternating current source through said second rectifier and said firstresistor to apply an operating voltage to said relay winding and closesaid contact, second circuit means connecting said half-wave rectifierand said first capacitor in series with each other and with saidhalf-wave rectifier and said first capacitor connected across said relaywinding, said third resistor being connected across said firstcapacitor, said half-wave rectifier being polarized to pass chargingcurrent from said second rectifier to said first capacitor uponenergization of said first and second circuit means for reducing thevoltage across said relay winding to delay the operation of the relayand the closing of said relay contact until said first capacitor ischarged to a voltage sufficient to operate said relay, third circuitmeans controlled by operation of said closed contact for directingcurrent from said source through said first and second resistors todecrease the voltage applied to said relay winding from said source to avalue less than the operating voltage but greater than the releasevoltage, said second capacitor assuring positive operation of said relayand the maintenance of said closed conact at said decreased voltage,said decreased voltage across said relay Winding causing said firstcapacitor to discharge, said polarized half-wave rectifier preventingdischarge current of said first capacitor from traversing said relaywinding and directing said discharged current to flow through said thirdresistor, said second and third circuit means establishing a steadystate voltage condition approaching that of the release voltage of therelay and thereby providing a rapid release of said relay upon deenerg'ization of said first circuit means and also providing a delay tothe operation of the relay by a re-ch'arging of said first capacitorupon re-energization of said first circuit means.

2. In combination, a relay having a winding and a contact, said relaybeing operable to close said contact when the voltage across saidwinding is of an operating value and being operable to open said contactwhen the voltage across said winding is below a release value, ahalf-wave rectifier, a second rectifier, a first capacitor, a secondcapacitor connected across said relay Winding, a first resistorconnected between said second rectifier and said source, a secondresistor, and a third resistor, first circuit means for energizing s'aidrelay winding and said second capacitor from an alternating currentsource through said second rectifier and said first resistor to apply anoperating voltage to said relay winding and close said contact, secondcircuit means connecting said half-wave rectifier and said firstcapacitor in series with each other and with said half-wave rectifierand said first capacitor connected across said relay winding, said thirdresistor being connected across said first capa'ctor, said half-waverectifier being polarized to pass charging current from said secondrectifier to said first capacitor upon energization of said first andsecond circuit means for reducing the voltage across said relay windingto delay the operation of the relay and the closing of said relaycontact until said first capacitor is charged to a voltage sufiicient tooperate said relay, third circuit means controlled by operation of saidclosed contact for directing current from said source through said firstand second resistors to decrease the voltage applied to said relaywinding from said source to a value less than the operating voltage butgreater than the release voltage, said second capacitor assuringpositive operation of said relay and the maintenance of said closedcontact at said decreased voltage, said decreased voltage across saidrelay winding causing said first capacitor to discharge, said polarizedhalf-wave rectifier preventing discharged current of said firstcapacitor from traversing said relay winding and directing saiddischarged current to flow through said third resistor, said second andthird circuit means establishing a steady state voltage conditionapproaching that of the release voltage of the relay and therebyproviding a rapid release of said relay upon de-energization of saidfirst circuit means and also providing a delay to the operation of therelay by a recharging of said first capacitor upon re-energization ofsaid first circuit means.

3. In combination, a relay having a winding and a contact, said relaybeing operable to close said contact when the voltage across saidwinding is of an operating value and being operable to open said contactwhen the voltage across said winding is below a release value, ahalfwave rectifier, a second rectifier, a first capacitor, a secondcapacitor connected across said relay winding, a first resistorconnected between said second rectifier and said relay winding, a secondresistor, and a third resistor, first circuit means for energizing saidrelay winding and said second capacitor from an alternating currentsource through said second rectifier and said first resistor to apply anoperating voltage to said relay winding and close said contact, secondcircuit means connecting said halfwave rectifier and said firstcapacitor in series with each other and with said half-wave rectifierand said first capacitor connected across said relay winding, said thirdresistor being connected across said first capacitor, said halfwaverectifier being polarized to pass charging current from said secondrectifier to said first capacitor upon energization of said first andsecond circuit means for reducing the voltage across said relay windingto delay the opera tion of the relay and the closing of said relaycontact until said first capacitor is charged to a voltage sufiicient tooperate said relay, third circuit means controlled by operation of saidclosed contact for directing current from said source through said firstand second resistors to decrease the voltage applied to said relaywinding from said source to a value less than the operating voltage butgreater than the release voltage, said second capacitor assuringpositive; operation of said relay and the maintenance of said closedcontact at said decreased voltage, said decreased Voltage across saidrelay winding causing said first capacitor to discharge, said polarizedhalf-wave rectifier preventing discharged current of said firstcapacitor from traversing said relay winding and directing saiddischarged current to flow through said third resistor, said second andthird circuit means establishing a steady state voltage conditionapproaching that of the release voltage of the relay and therebyproviding a rapid release of said relay upon de-energization of saidfirst circuit means and also providing a delay to the operation of therelay by a re-charging of said first capacitor upon re-energization ofsaid first circuit means.

4. In combination, a relay having a winding and' contact means, saidrelay being operable when the voltage across said winding is of anoperating value and being releasable when the voltage across saidwinding is below a release value, a rectifier, a capacitor, a firstresistor, a second resistor, and a third resistor, first circuit meansfor energizing said relay winding from a current source through saidfirst resistor to apply an operating voltage to said relay winding,second circuit means connecting said rectifier and said capacitor inseries with each other and with said rectifier and said capacitorconnected across said relay winding, said third resistor being connectedacross said capacitor, said rectifier being polarized to pass chargingcurrent from said source to said capacitor for reducing the voltageacross said relay winding to delay the operation of said relay and saidcontact means until said capacitor is charged to a value sufiicient tooperate said relay, third circuit means controlled by said contact meansupon operation of said relay for directing current through said secondresistor to decrease the voltage applied to said relay winding from saidsource to a value less than the operating voltage but greater than therelease voltage, said decreased voltage across said relay windingcausing said capacitor to discharge, said polarized rectifier preventingdischarged current of said capacitor from traversing said relay windingand directing said discharged current to flow through said thirdresistor, said second and third circuit means establishing a steadystate voltage condition approaching that of the release voltage of therelay and thereby providing a rapid release of said relay uponde-energization of said first circuit means and also providing a delayto the operation of the relay by a recharging of said capacitor uponre-energization of said first circuit means.

5. In combination, a relay having a winding and contact means, saidrelay being operable when the voltage across said winding is of anoperating value and being releasable when the voltage across saidwinding is below a release value, a rectifier, a capacitor, a firstresistor, a second resistor connected in series with said winding andshunted by said contact means, and a third resistor, first circuit meansfor energizing said relay winding from a current source through saidfirst resistor to apply an operating voltage to said relay winding,second circuit means connecting said rectifier and said first capacitorin series with each other and with said rectifier and said capacitorconnected across said relay winding, said third resistor being connectedacross said capacitor, said rectifier being polarized to pass chargingcurrent from said source to said capacitor for reducing the voltageacross said relay winding to delay the operation of said relay and saidcontact means until said capacitor is charged to a value sufiicient tooperate said relay, third circuit means controlled by said contact meansupon operation of said relay for directing current through said secondresistor to decrease the voltage applied to said relay winding from saidsource to a value less than the operating voltage but greater than therelease voltage, said decreased voltage across said relay Windingcausing said capacitor to discharge, said polarized rectifier preventingdischarged current of said capacitor from traversing said relay windingand directing said discharged current to flow through said thirdresistor, said second and third circuit means establishing a steadystate voltage condition approaching that of the release voltage of therelay and thereby providing a rapid release of said relay uponde-energization of said first circuit means and also providing a delayto the operation of the relay by a recharging of said capacitor uponre-energization of said first circuit means.

6. In combination, a relay having a winding and con tact means, saidrelay being operable when the voltage across said winding is of anoperating value and being releasable when the voltage across saidwinding is below a release value, a rectifier, a first capacitor, and asecond capacitor connected across said relay winding, a first resistor,21 second resistor connected in series with said winding and shunted bysaid contact means, and a third resistor, first circuit means forenergizing said relay winding from a current source through said firstresistor to apply an operating voltage to said relay Winding and saidsecond capacitor, second circuit means connecting said rectifier andsaid first capacitor in series with each other and with said rectifierand said first capacitor connected across said relay winding, said thirdresistor being connected across said first capacitor, said rectifierbeing polarized to pass charging current from said source to said firstcapacitor for reducing the voltage across said relay winding to delaythe operation of said relay and said contact means until said firstcapacitor is charged to a value sufiicient to operate said relay, thirdcircuit means controlled by said contact means upon operation of saidrelay for directing current through said second resistor to decrease thevoltage applied to said relay Winding from said source to a value lessthan the operating voltage but greater than the release voltage, saiddecreased voltage across said relay winding causing said first capacitorto discharge, said polarized rectifier preventing discharge current ofsaid first capacitor from traversing said relay winding and directingsaid discharge current to fiow through said third resistor, said secondand third circuit means establishing a steady state voltage conditionapproaching that of the release voltage of the relay and therebyproviding a rapid release of said relay upon deenergization of saidfirst circuit means and also providing a delay to the operation of therelay by a recharging of said first capacitor upon re-energization ofsaid first circuit means.

References Cited in the file of this patent UNITED STATES PATENTS2,293,425 Damrnond Aug. 18, 1942 2,307,576 DeCroce Jan. 5, 19432,509,252 Salazar May 30, 1950 FOREIGN PATENTS 625,128 Great BritainJune 22, 1949 986,551 France Mar. 28, 1951 754,059 Germany July 5, 1954

